BrowserTools

MP4 to MP3 Converter

Extract audio tracks from video files

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-02
Free Private No uploads

The engine is a WebAssembly build of FFmpeg that this page pulls from unpkg.com — about 30 MB — the first time you convert, and reuses from the browser cache afterwards. Your video is read into that in-process engine and is never uploaded.

What is MP4 to MP3 Converter?

Drop a video on this page and you get its sound as a standalone MP3 at 128, 192 or 320 kbps, with 192 kbps as the default. It is a genuine conversion rather than a stream copy: the audio is demuxed, decoded to uncompressed samples and re-encoded with LAME, so an AAC or Opus soundtrack is genuinely rebuilt as MP3. Bitrate is constant, which means you can predict the result size in advance — 192 kbps costs roughly 1.4 MB for every minute of audio, 128 kbps about 1 MB, and 320 kbps about 2.4 MB. Audio-only files go through the same path as video, so this doubles as an M4A or WAV to MP3 converter when you need it.

Extract the audio track from an MP4 video and save it as an MP3 file, entirely inside your browser using WebAssembly. No file size limits, no uploads, no accounts.

Private MP4 to MP3 Converter In Your Browser

MP4 to MP3 Converter is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use MP4 to MP3 Converter

1

Drag an MP4, MOV, MKV, WebM, AVI or audio file onto the drop area, or click it to open a file browser.

2

Pick a target from the Audio Bitrate row: 128 kbps (Light), 192 kbps (Standard) or 320 kbps (High Fidelity).

3

Press Extract MP3 and wait. On a cold browser cache the engine has to arrive first; afterwards the encode begins almost straight away.

4

Check the result in the built-in audio player, compare the Original and Result byte counts, then press Download MP3.

Key Capabilities
  • Constant-bitrate MP3 output at 128, 192 or 320 kbps, with 192 kbps preselected.
  • Takes video and audio sources alike — MP4, MOV, MKV, WebM, AVI, M4A, WAV, OGG, FLAC and Opus all demux through the same engine.
  • Reports source and result file sizes side by side, so the bitrate arithmetic is visible rather than implied.
  • Produces the download in memory as a Blob; the input file is read locally and never transmitted.
Common Use Cases
  • A podcast editor lifting the clean music bed out of a camera-mastered interview before laying narration over it.
  • A course creator who needs a two-hour lecture recording turned into an MP3 small enough to email to students.
  • A musician checking how a finished mix survives an MP3 encode, to hear the artefacts a streaming listener will get.
Clear Answers

Frequently Asked Questions

Is this a real conversion or just the existing stream in a new wrapper?
A real conversion. The audio is decoded and re-encoded with LAME, which is the only reason you can choose a bitrate at all. A stream copy would be quicker and bit-perfect, but it could only ever hand back the codec already sitting in the file.
Why does the very first conversion take so long?
The first run has to bring down a media engine before a single sample is touched: roughly 30 MB of FFmpeg compiled to WebAssembly arrives from unpkg.com. Your browser then holds on to it, so the second conversion onwards starts immediately. A long 4K file still takes a while after that, because encoding is real CPU work and is not instant.
Does going to MP3 damage the sound?
Yes, by design — MP3 is lossy. The damage compounds if you convert an existing 128 kbps MP3 up to 320 kbps, because the extra bits cannot reconstruct what the first encode discarded. If you need a clean copy for editing, ask for WAV instead.
Can I get a mono file out of a stereo source?
Not from this page. There is no channel control here, so the output inherits whatever layout the source had. A mono voice recording comes back mono; a stereo mix comes back stereo.